Question

For a touring bicyclist the drag coefficient (where )is 1.02, the frontal area is 0.467 , and the coefficient of rolling
frictionis 4.70×10−3. The rider has mass52.0 , and her bike has mass 13.0 . Take the free fall acceleration to
be = 9.80 and the density of air to
be = 1.20 .

a)To maintain a speed of 12.9 on a level road, what must the
rider'spower output to the rear wheel be?

b)For racing, the same rider uses a different bike with
acoefficient of rolling friction 3.20×10−3and mass 8.90
. She also crouches down,
reducing her dragcoefficient to 0.940 and reducing her frontal area
to0.365 . What must her power output to the
rearwheel be then to maintain a speed of 12.9 ?

c)For the situation in part (b), what power output is required
tomaintain a speed of 6.00 ? (For more on aerodynamic
speedlimitations for a wide variety of human-powered vehicles see
"TheAerodynamics of Human-Powered Land Vehicles,"
ScientificAmerican, December, 1983.)